1. Field of the Invention
The present invention relates, in general, to a microwave oven, and more particularly, to a microwave oven and control unit thereof.
2. Description of the Related Art
A microwave oven emits microwaves of 2450 MHz generated by a magnetron onto food and heats the food. When microwaves vibrate molecules of the food, heat is generated due to collisions between the molecules, so that the food is cooked by the heat.
FIG. 1 is a block diagram showing a construction of a conventional microwave oven. As shown in FIG. 1, a control unit 102 controls an overall operation of the microwave oven. An input unit 104 and an external memory 106 are connected at input terminals of the control unit 102. The input unit 104 is provided with cooking mode setting buttons and numeral buttons to set cooking modes, cooking time, etc. The external memory 106 stores cooking data of each of the cooking modes. The control unit 102 has a magnetron drive unit 108, a fan drive unit 112, a tray motor drive unit 116 and a display drive unit 120 connected to output terminals of the control unit 102. The magnetron drive unit 108 drives a magnetron 110 to generate microwaves. The fan drive unit 112 drives a cooling fan 114 to cool various kinds of electrical devices installed in a machine room of the microwave oven. The tray motor drive unit 116 drives a tray motor 118 to rotate a tray (not shown) disposed in a cooking room. The display drive unit 120 drives a display unit 122 to display a help menu and cooking information of the cooking modes, and to set specific values.
In the conventional microwave oven, a control panel installed in the input unit 104 is a membrane switch control panel which is based on a control panel using mechanical switches. Recently, the control panel has been implemented as a touch screen control panel using a Liquid Crystal Display (LCD).
When the control panel is implemented as the membrane switch control panel, it allows various visual designs compared to the control panel using mechanical switches. Thus, an appearance of the membrane switch control panel may be designed to be attractive.
Additionally, life of the control panel using mechanical switches is not long due to a mechanical abrasion of the mechanical switches. In contrast, the membrane switch control panel is semi-permanent because a circuit and contact points are formed on two or more films, and electrical contact between the contact points is used. Further, films forming membrane switches are very thin, so that the membrane switch control panel may be manufactured to be thinner than the control panel using the mechanical switches.
However, the membrane switch control panel may not overcome the limits of low practical uses of the conventional control panel using the mechanical switches. One function is allocated to each of the mechanical and membrane switches. Thus, a number of switches corresponding to respective functions may not be proportional to an increase in the functions to be implemented in the microwave oven. Since an area of the control panel of the microwave oven is limited, a number of installable switches is limited in the control panel using mechanical switches and the membrane switch control panel.
The touch screen control panel using the LCD provides unlimited input or setting functions on a control panel having a limited area. If a user touches switches or buttons displayed on a screen of the LCD, a signal allocated to a corresponding switch or button is transmitted to the control unit 102. That is, a main menu or main functions are allowed to be displayed and selected on an initial screen of the LCD. Sub-menu or sub-functions corresponding to the main menu or main functions, respectively, are displayed on another screen and arranged to be hierarchical based on necessity, so that almost unlimited menus or functions are able to be implemented using the touch screen control panel.
Even if the hierarchical construction of the menus using the LCD is almost unlimited, it needs to be limited so that the user is not inconvenienced when cooking food in the microwave oven. That is, if the microwave oven is constructed so that an advanced function may not be used until a user reaches a sub-menu to select a specific sub-function through several steps, the user may experience extreme inconvenience in using the function such that the user may ignore the function.
Accordingly, it is preferable that another switch or button to perform basic functions of the microwave oven, such as power ON/OFF, cooking start and temporary stop, is provided without displaying the functions using the LCD. Further, the membrane switch control panel may be manufactured in only a flat form due to its structural characteristics. Accordingly, it is difficult to develop various designs to correspond to demands of the user using the membrane switch control panel.
The conventional microwave oven generally uses a Complex Instruction Set Computer (CISC) microprocessor. For this reason, a microprocessor has to be additionally installed to add a new function to the microwave oven, requiring a new control panel to be designed and increasing cost of the microwave oven.